In recent years, in response to increasing concern of consumers about food allergy problems, it is recommended to provide food packages or the like with labels indicating that ingredients which cause food allergy are contained. In particular, with regard to seven items consisting of wheat, buckwheat, eggs, milk, peanuts, shrimps, and crabs, all of which are to be highly required to label in consideration of the number of cases of allergy and their seriousness, thus mandatory labeling of foods containing those ingredients is required for manufacturers under the Food Sanitation Law as well.
Further, labeling indicating “containing a specified ingredient”, “containing no specified ingredient”, or the like provides a benefit for manufacturers as well because the labeling allows consumers to receive their products without anxiety.
In a processed food to be manufactured by mixing various ingredients, since tracing of records for individual ingredients is complicated, it is desirable to be able to directly inspect a manufactured product. Further, the contamination of a substance, which is not used as an ingredient, may occur in a manufacturing line. Thus, from the viewpoints of the operation and maintenance of a product and the prevention of an unforeseen accident, there is a demand to provide a food inspection method that can be utilized in a quick and simple manner even in manufacturing plants, and that can detect with good accuracy whether a food contains a specified ingredient or not.
In the case of a processed food, even in a component derived from the same ingredient, there is a problem in that, in some manufacturing conditions, a substance contained in a specified ingredient of interest for inspection is insolubilized and hence is hardly extracted. In baked confectionery and the like, a protein is hardly extracted because heating denatures the protein and thiol groups form an S—S bond. Further, it is also conceivable that a substance contained in a specified ingredient of interest for inspection interacts with other components compounded in a processed food, and is insolubilized, resulting in poor extraction efficiency.
The poor extraction efficiency during preparation of an extract from a food is not preferred in consideration of a demand to detect a specified ingredient of interest for inspection with good accuracy. Further, it is also conceivable that the poor extraction efficiency generates variations in the inspection results.
In order to deal with the above-mentioned problems, for example, Patent Document 1 below discloses an invention of a food component extractant characterized by containing a reducing agent and a solubilizer. Further, the patent document describes that the incorporation of a reducing agent for changing a protein structure, and a solubilizer made up of a surfactant, urea, and the like into an extractant enables a denatured and/or non-denatured protein to be extracted with higher efficiency than ever before.
In addition, there is known, in immunochromatography out of immunological measurement methods, a phenomenon called a “prozone phenomenon” in which a measurement value is lowered when a substance (antigen) of interest for inspection exists in an excessive amount with respect to the amount of an antibody to be used. Owing to the prozone phenomenon, there has been a problem in that, when a sample contains a substance (antigen) of interest for inspection in a large amount, the sample may be evaluated as false negative, with the result that the evaluation lacks reliability.
Patent Document 1: JP-A-2006-71509